How to create a custom join form

Hello does anyone know how to create a custom join form? I tried copying the current join form and renaming it join2.php and next I added it to the file admin/fields.php as the following:
<li><a href="#m1"        ><img src="images/join.png"   />Join Form       </a></li>
<li><a href="#edit_tab"  ><img src="images/edit.png"   />Edit Profile    </a></li>
<li><a href="#view_tab"  ><img src="images/view.png"   />View Profile    </a></li>
<li><a href="#search_tab"><img src="images/search.png" />Search Profiles </a></li>
<li><a href="#join2.php"><img src="images/join2.png" />Join2 Form  </a></li>

it displayed in my "fields builder" but when I clicked on the tab it would revert back to only reading the original join.php form. Is the a specific field that I need to change to make it see the join2.php? My goal is to make different o=join forms for different members. For example, artist they can only add pictures and producers they can add pictures and videos.